1. Field of the Invention
The present invention relates to a valve timing control device of an internal combustion engine, which controls open/close timing of intake and/or exhaust valves of the engine.
2. Description of the Related Art
In order to clarify the features of the present invention, one known art in the field of the present invention, which is disclosed in Japanese Laid-open Patent Application (tokkai) 2013-36401, will be briefly described in the following.
The valve timing control device disclosed in the Japanese publication is of an electric type and generally comprises an electric motor whose cylindrical motor housing is integrally connected to a timing sprocket and a cup-shaped cover member that is arranged to cover a front part of the cylindrical motor housing. In an annular gap defined between a cylindrical inner surface of a stepped annular part formed on the cup-shaped cover member and an outer cylindrical surface of the cylindrical motor housing, there is disposed an annular oil seal.
The annular oil seal is constructed mainly from a synthetic rubber. Upon coupling of the oil seal with the annular gap, an outer solid rubber part (or base portion) of the annular oil seal is pressed onto the cylindrical inner surface of the stepped annular part, and at the same time an inner rubber part of the annular oil seal that includes an annular seal portion with a seal lip is slidably pressed onto the outer cylindrical surface of the cylindrical motor housing. The annular seal portion is biased toward the outer cylindrical surface of the motor housing by a back-up spring.
Because of provision of the annular oil seal arranged in the above-mentioned manner, the annular gap can be sealed and thus, any oil splashed by the timing sprocket is prevented from entering into the motor housing from a front side of the electric motor.